Earthquake Risks

Earthquake Risks

By David Lewis

​Student Learning Objective: Students will be able to explain why some areas are more likely to experience an earthquake than others and how we measure Earthquakes.

Open Ended

Where do Earthquakes occur?

Where do Earthquakes occur?

• ​Few earthquakes occur in the middle of a continent. Most earthquakes occur in the oceans and along the edges of continents where tectonic plates meet.

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How are Earthquakes measured?

• ​The Richter Magnitude Scale - a numerical rating system that measures the energy, or magnitude, of the largest seismic waves produced by an Earthquake.

• ​The Moment Magnitude Scale​ - a rating scale that measures the energy released by an Earthquake, taking into account the size of the fault that breaks, the motion that occurs along the fault and the strength of the rocks that break during an Earthquake.

How are Earthquakes measured?

• ​Another way to measure and describe an Earthquake is to evaluate the damage that results from shaking.

• Shaking is directly related to Earthquake intensity, or strength.

• The Modified Mercalli Intensity Scale​- measures Earthquake intensity based on descriptions of the Earthquake's effects on people and structures.

• The Modified Mercalli Intensity Scale ranges from I, when shaking is not noticeable, to XII, when everything is destroyed.​

Multiple Choice

If I wanted to measure and describe an Earthquake by evaluating the damage that results from shaking which Scale would I use?

• Richter Magnitude Scale

• Moment Magnitude Scale

• Modified Mercalli Intensity Scale

• ​Pancaking happens when the supporting walls of the ground floor of a building fail. This causes the upper floors to fall and collapse as they hit lower floors. The resulting debris resembles a stack of pancakes, so the process is called pancaking

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​What factors affect the amount of damage caused by an Earthquake?

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• Structural failure can result because of the height of a building. All structures have natural frequencies of vibration. Tall buildings sway with a natural period that depends on their heights and other factors. The higher the building, the longer its natural period of vibration is. Seismic waves with the same period as that of a tall building can cause the building to sway violently and collapse during an earthquake.

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​What factors affect the amount of damage caused by an Earthquake?

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Open Ended

What protects the Burj Khalifa from Earthquakes?

​Wet soil can be strong but the shaking from an earthquake can cause it to act more like a liquid. Liquefaction causes buildings to sink into soil and collapse.

​​Liquefaction

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​A landslide is the rapid downhill movement of soil, loose rocks, and boulders. In sloping areas, earthquakes can trigger massive landslides.

Landslides

​A large ocean wave generated by vertical motion of the seafloor during an earthquake. A tsunami can be created by an underwater earthquake.

Tsunami

​Land and Soil Failure

Open Ended

How can Scientists predict when an Earthquake will happen?